Re: [PATCH v1 4/4] riscv: dts: sifive unmatched: Add PWM controlled LEDs

[Geert Uytterhoeven]

Hi Emil,

On Tue, Jul 5, 2022 at 11:01 PM Emil Renner Berthing
<emil.renner.berthing@xxxxxxxxxxxxx> wrote:
> This adds the two PWM controlled LEDs to the HiFive Unmatched device
> tree. D12 is just a regular green diode, but D2 is an RGB diode with 3
> PWM inputs controlling the three different colours.
>
> Signed-off-by: Emil Renner Berthing <emil.renner.berthing@xxxxxxxxxxxxx>

Thanks for your patch!

> --- a/arch/riscv/boot/dts/sifive/hifive-unmatched-a00.dts
> +++ b/arch/riscv/boot/dts/sifive/hifive-unmatched-a00.dts
> @@ -44,6 +46,46 @@ gpio-poweroff {
>                 compatible = "gpio-poweroff";
>                 gpios = <&gpio 2 GPIO_ACTIVE_LOW>;
>         };
> +
> +       led-controller-1 {
> +               compatible = "pwm-leds";
> +
> +               led-d12 {
> +                       pwms = <&pwm0 0 7812500 PWM_POLARITY_INVERTED>;
> +                       active-low;

The first thing that came into my mind was "why not drop the
PWM_POLARITY_INVERTED flag instead?".

But it turns out drivers/pwm/pwm-sifive.c does not support
non-inverted PWMs, and returns -EINVAL if PWM_POLARITY_INVERSED
(no typo) is not set.  I think it would be good if
Documentation/devicetree/bindings/pwm/pwm-sifive.yaml would mention
this limitation, and perhaps even enforce it, if possible?

I didn't check this against the schematics, but the generic structure
LGTM, so
Reviewed-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds